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目前就软土基坑开挖卸荷对邻近桩基变形影响的研究一般是基于瞬时开挖工况,很少考虑时间效应对桩-土相互作用的影响,但实际工程中软土在开挖情况下具有较为明显的流变效应。从地基黏弹性角度出发,采用两阶段法研究了黏弹性地基中基坑开挖与邻近桩基相互作用的时域问题。第1阶段基于Boltzmann黏弹性模型推导出Mindlin时域解,用于分析黏弹性地基中基坑开挖引起的邻近桩基处的土体附加应力;第2阶段采用Pasternak地基模型分析桩基与黏弹性土体之间的相互作用,并求得考虑流变效应的桩基水平变形的简化时域解。最后,采用大型有限差分软件对相关工况进行数值模拟,并将数值模拟结果与简化时域解进行对比分析,得到了较好的一致性。此外,也针对Boltzmann黏弹性模型参数(体积模量、剪切模量、黏性系数)、桩径、基坑开挖深度、桩与基坑间距和基坑开挖尺寸进行了影响因素分析。分析结果表明,所得出的简化时域解能较好地反映基坑开挖对邻近桩基水平变形的影响,以及桩基变形随时间的发展趋势,可为相关实际工程提供一定理论依据。
At present, the research on the effect of soft soil foundation excavation unloading on the deformation of adjacent pile foundation is generally based on transient excavation conditions, seldom consider the effect of time effect on the pile-soil interaction. However, in practical engineering, The case has a more obvious rheological effect. From the view of viscoelasticity, the two-stage method is used to study the time-domain problem of the interaction between the foundation pit and the adjacent pile foundation in viscoelastic foundation. In the first stage, the Mindlin time-domain solution is deduced based on the Boltzmann viscoelastic model, which is used to analyze the additional stress of the soil near the pile foundation caused by excavation in the viscoelastic foundation. In the second stage, the foundation is analyzed by using the Pasternak foundation model Elastic soil, and obtain the simplified time-domain solution of pile foundation horizontal deformation considering rheological effect. Finally, large-scale finite-difference software is used to simulate the relevant operating conditions, and the numerical simulation results are compared with the simplified time-domain solution to obtain better consistency. In addition, the influence factors of Boltzmann viscoelastic model parameters (bulk modulus, shear modulus, viscous coefficient), pile diameter, excavation depth, spacing between piles and foundation pit and excavation size are also analyzed. The analysis results show that the simplified time-domain solutions obtained can well reflect the influence of excavation on the horizontal deformation of adjacent pile foundations and the development trend of pile deformation with time, which can provide some theoretical basis for related practical projects.